error: lifetime may not live long enough --> $DIR/issue-28848.rs:10:5 | LL | pub fn foo<'a, 'b>(u: &'b ()) -> &'a () { | -- -- lifetime `'b` defined here | | | lifetime `'a` defined here LL | Foo::<'a, 'b>::xmute(u) | ^^^^^^^^^^^^^^^^^^^^ requires that `'b` must outlive `'a` | = help: consider adding the following bound: `'b: 'a` error: aborting due to previous error